Little evidence to support most dietary interventions for psoriasis

06/28/2018

By Marilynn Larkin

NEW YORK (Reuters Health) - New recommendations from the National Psoriasis Foundation Medical Board suggest that losing weight by following a low-calorie diet can reduce psoriasis severity in overweight patients, but there is little evidence to support other dietary interventions.

"Our psoriasis patients have long asked us about the role of diet on psoriasis," Dr. April Armstrong of the University of Southern California, Los Angeles told Reuters Health. "This pivotal effort from the National Psoriasis Foundation is a few years in the making."

"We found that weight reduction with a diet low in calories is helpful in reducing psoriasis severity in overweight psoriasis patients," she said by email. "A gluten-free diet is not helpful for everyone...It can be helpful in reducing psoriasis in patients whose blood tests are positive for gluten sensitivity."

To develop the recommendations, Dr. Armstrong and colleagues searched the literature from 2014 to August 31, 2017 for studies that evaluated the impact of diet on psoriasis or psoriatic arthritis.

They identified 55 studies including 77,557 participants, of which 4,534 were diagnosed with psoriasis. Although a small number of pediatric patients were included in some studies, they noted, available data are insufficient to make recommendations for children.

The strength of the recommendations was determined by the level of evidence.

As reported online June 20 in JAMA Dermatology, the team made the following recommendations:

- Dietary weight reduction with a low-calorie diet is strongly recommended for overweight and obese patients with psoriasis.

- A gluten-free diet is strongly recommended only for those with confirmed celiac disease.

- A three-month trial of a gluten-free diet as an adjunct to standard medical care is weakly recommended for those who test positive for serological markers of gluten sensitivity; however, universal screening for those markers is not recommended because of the high rate of false positives.

- Oral fish oil supplementation is not recommended for psoriasis because it was not effective at the examined doses and durations; evidence on intravenous supplementation is too limited to make a recommendation

- Neither vitamin D nor vitamin B supplementation is recommended.

- Selenium is not recommended for the treatment of plaque psoriasis.

- No recommendation can be made for micronutrient supplementation because of insufficient evidence.

- Low-quality evidence suggests that psoriasis patients may consider a trial of a Mediterranean diet and/or a trial of consuming more foods with omega-3 fatty acids and fiber, and fewer calories, fatty acids and simple carbohydrates.

"There is little evidence to support many diets and nutritional supplements that have been touted to be useful in reducing psoriasis," Dr. Armstrong stressed. "Thus, while certain diets can be helpful in selected patients, it is the medical therapies that make the larger difference."

Dr. Daniel Aires, a dermatologist at the University of Kansas Health System, said in an email to Reuters Health, "Nutritional guidelines can be helpful. Furthermore, there is very little harm in trying most of these interventions, such as reducing weight if overweight, taking vitamin D, eating a Mediterranean diet, and supplementing with high quality fish oil.

However, like Dr. Armstrong, he said that "patients with psoriasis in skin and joints should not expect dietary modification to replace medical therapy."

"Few of us get enough sun or drink enough milk, so (in our practice) we recommend vitamin D supplementation for nearly all patients who don't have contraindications such as kidney stones," said Dr. Armstrong, who was not involved in developing the recommendations.

"I have seen many patients take off and keep off weight with low-carbohydrate diets," he noted. "For fish oils I recommend high quality supplements that need to be refrigerated."

"Patients appreciate dietary counseling as part of a complete program, including medications and lifestyle changes that also include exercise and stress reduction," Dr. Aires concluded.